You can't "close up" software that was free. The software remains free.
The only freedom the allegedly "more open" licenses give developers is to deny freedoms to their users.
It gives developers the freedom to create an aggregate product without also releasing their own code under the GPL, allowing them to pursue a business model that they feel will fund the ongoing R&D necessary to produce that product.
For the users (and software freedom is about them), those licenses give nothing.
If users do not feel that a product does not provide a fair trade, they are under no obligation to purchase or use it, and the original code remains to do with what they will. However, as indicated by vast market success, users do feel that these licenses and the products produced using them do provide something of value.
What GPL prevents that BSD doesn't is closed forks. Obviously some people don't care about closed forks --- some people may even like them on principle --- or nobody would BSD-license anything.
It's far too common that the person who assigns value to software and that signs the check is not the same person who puts it to work.
Well -- I for one am happy with the licensing status of Mac OS X, and think I've received a perfectly fair trade.
My wife had to build an intranet on top of Sharepoint because a PHB said so. I have to read my e-mails off an Exchange server because corporate IT finds it nice. Far too many servers are Red Hat while I would prefer Debian (I am a fan of APT). Perhaps you have to make your presentations on PowerPoint for Mac, even knowing how much better they would look with Keynote. Life's not perfect.
And, while I love the NeXT side of OSX, I find the Unix side far too early 90's for my taste ;-)
If that's what they need, perhaps to migrate their products to a BSD-licensed RDBMS like PostgreSQL. Or to a public-domain one like SQLite. Or a fully proprietary one. It's their software and, since, they have already licensed it as proprietary, their users were already robbed the freedoms GPL'ed MySQL would provide.
As it is now, those companies have licenses for specific versions. If they didn't get permanent unrevokable licenses and were happy with the cheaper ones they got, well... Phineas Barnum would be happy to use them as examples.
"whether this is fair is up for debate"
If handing over copyright is too expensive, companies are always free not to contribute or not to use Asterisk at all. They will, however, have to compete with other companies who do. Economics will dictate who wins.
"(and is partly why many users hate gpl software, preferring more "open" licenses like bsd/isc)"
The only freedom GPL denies a developer is to close up software that was once free. The only freedom the allegedly "more open" licenses give developers is to deny freedoms to their users. For the users (and software freedom is about them), those licenses give nothing.
But we are drifting from the original topic.
The topic is that MySQL is Oracle-proof and doesn't need saving the same way other GPL'ed products don't need saving. They are either good - and thus worthy of surviving - or bad - and thus will die natural deaths.
Many people have emotional attachment to their software. I must confess I am thinking and rethinking moving from Linux to OpenSolaris for much too long to explain it in strictly rational terms. I will miss it when Linux dies, but, by then, I expect GNU/HURD to run nicely on my 64-core ARM-based netbook. Or, at least, ZFS to be under GPLv3.